Lumbar Spine Anatomy

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Questions and Answers

What is the main reason for the massive body of the typical lumbar vertebra?

To support compressive loads caused by body weight and ground reaction forces (correct)

To facilitate the movement of the upper limbs

To provide flexibility to the lumbar spine

To protect the spinal cord from injury

What is the orientation of the superior articular facets in the upper lumbar region?

Parallel to the sagittal plane

Approximately midway between the sagittal and frontal planes

Perpendicular to the sagittal plane

Closest to the sagittal plane (correct)

What is the shape of the inferior articular facets?

Vertical and convex (correct)

Horizontal and flat

Moderately concave

Oblong and irregular

What is the function of the mamillary processes?

To provide attachment for the multifidus and medial intertransverse muscles Signup and view all the answers

What is the direction of the pedicles in the lumbar vertebra?

Posterolaterally Signup and view all the answers

What is the shape of the vertebral canal in the lumbar region?

Triangular Signup and view all the answers

What is the characteristic of the laminae in the lumbar vertebra?

Short and thick Signup and view all the answers

What is the main function of the transverse process in the lumbar vertebra?

To provide attachment for muscles Signup and view all the answers

What is the shape of the vertebral foramen in the 5th lumbar vertebra?

Triangular Signup and view all the answers

What is the function of the accessory processes?

To provide attachment sites for muscles Signup and view all the answers

What is the shape of the body of the 5th lumbar vertebra?

Wedge-shaped Signup and view all the answers

What is the orientation of the apophyseal joints in the L5/S1 region?

Frontal plane Signup and view all the answers

What is the function of the L5–S1 apophyseal joints?

To provide anterior-posterior stability Signup and view all the answers

What is the shape of the spinous process in the 5th lumbar vertebra?

Broad and thick Signup and view all the answers

What is the characteristic of the transverse process in the 5th lumbar vertebra?

Long and slender Signup and view all the answers

What is the lumbosacral joint formed by?

Two separate articulations Signup and view all the answers

What is the lumbosacral joint characterized as?

The most unstable segment of the lumbar spine Signup and view all the answers

What is the force that acts perpendicular to the upper surface of S1?

N Signup and view all the answers

What is the result of the fracture of the isthmus in the pars interarticularis?

Spondylolysis Signup and view all the answers

What is the direction of the force G?

Parallel to the upper surface of S1 Signup and view all the answers

What happens to the body of L5 when the arch is no longer retained posteriorly on the superior articular processes of the sacrum?

It glides inferiorly and anteriorly Signup and view all the answers

What is the term for the condition when the body of L5 glides inferiorly and anteriorly?

Spondylolisthesis Signup and view all the answers

What are the structures that still retain L5 on the sacrum and prevent further slippage?

The lumbosacral intervertebral disc and the paravertebral muscles Signup and view all the answers

What is the cause of the pain associated with spondylolisthesis?

The spasm of the paravertebral muscles Signup and view all the answers

What type of joints are formed between the articular processes of L5 and S1 vertebrae?

Zygapophysial joints Signup and view all the answers

Where are the facets of S1 positioned?

Posteromedially Signup and view all the answers

What movements occur in the lumbosacral joint?

Flexion, extension, and lateral flexion Signup and view all the answers

What is the angle formed by the first sacral segment with the horizontal called?

Lumbosacral angle Signup and view all the answers

What happens to the lumbar curve when the lumbosacral angle increases?

It increases Signup and view all the answers

What type of stress increases at the lumbosacral joint when the lumbosacral angle increases?

Shearing stress Signup and view all the answers

Which vertebrae form the lumbosacral articulation?

L5 and S1 Signup and view all the answers

What affects the superimposed lumbar curvature?

Pelvic position Signup and view all the answers

Where does the lateral lumbosacral ligament arise from?

Transverse process of L5 vertebra Signup and view all the answers

What is the posterior layer of the thoracolumbar fascia continuous with?

Sacrotuberous ligament Signup and view all the answers

What muscles arise from the lateral raphe?

Internal abdominal oblique and transversus abdominal Signup and view all the answers

What is the ligament stability of the lumbar spine related to?

Thoracolumbar fascia Signup and view all the answers

What is the lateral lumbosacral ligament partially continuous with?

Iliolumbar ligament Signup and view all the answers

Where does the posterior layer of the thoracolumbar fascia arise from?

Spinous processes and supraspinous ligaments of the thoracic, lumbar, and sacral spines Signup and view all the answers

What is the middle layer of the thoracolumbar fascia formed from?

The posterior layer Signup and view all the answers

What is the lateral lumbosacral ligament attached to?

Ala of the sacrum Signup and view all the answers

What is the posterior layer of the thoracolumbar fascia large and?

Thick and fibrous Signup and view all the answers

What is the lateral lumbosacral ligament blended with at its insertion?

Anterior sacroiliac ligament Signup and view all the answers

Study Notes

Typical Lumbar Vertebrae

The body of the typical lumbar vertebra is massive, with a transverse diameter greater than the anterior diameter and height.
The size and shape reflect the need to support great compressive loads caused by body weight, ground reaction forces, and muscle contraction.
Laminae and pedicles are short and thick, forming the posterior and lateral walls of the nearly triangular vertebral canal.
Pedicles are short and thick, project posterolaterally.
Laminae are short and broad.
Superior articular (zygapophyseal) facets are moderately concave, facing medial to posterior-medial.
Inferior articular (zygapophyseal) facets are vertical and convex, facing slightly anteriorly and laterally.
Mamillary processes, small bumps, are located on the posterior edge of each superior articular facet and serve as attachment for the multifidus and medial intertransverse muscles.

Transverse Process

The transverse process is long and slender and extends horizontally.
Accessory processes, small and irregular bony prominences, are located on the posterior surface of the transverse process near its attachment to the pedicle.
Accessory processes serve as attachment sites for the multifidus and medial intertransverse muscles.

Spinous Process

The spinous process is broad and thick and extends horizontally.

Vertebral Foramen

The vertebral foramen is triangular and larger than the thoracic vertebral foramen but smaller than the cervical vertebral foramen.

5th Lumbar Vertebra

The fifth lumbar vertebra is a transitional vertebra and differs from the rest of the lumbar vertebrae.
The body of the vertebra is wedge-shaped, with the anterior portion being of greater height than the posterior portion.
The L5/S1 lumbosacral disk is also wedge-shaped.
The inferior articular facets of L5 articulate with the superior articular facets of the sacrum.
Apophyseal joints are typically oriented much closer to the frontal plane than the other lumbar articulations.
The L5–S1 apophyseal joints provide an important source of anterior-posterior stability to the lumbosacral junction.

Lumbosacral Joint

The lumbosacral joint is formed by two separate articulations: the anterior intervertebral joint and the apophyseal joints.
The lumbosacral joint is the most unstable segment of the lumbar spine.

Forces Acting on the Lumbosacral Joint

The weight (P) can be resolved into two forces: a force (N) acting perpendicular to the upper surface of S1 and a force (G) acting parallel to the upper surface of S1 and pulling L5 anteriorly.
These forces are transmitted through a single point in the pars interarticularis.

Lumbosacral Angle

The lumbosacral angle is the angle formed by the first sacral segment and the horizontal.
The size of the angle varies with the position of the pelvis and affects the superimposed lumbar curvature.
An increase in this angle will result in an increase in lordosis of the lumbar curve and will increase the amount of shearing stress at the lumbosacral joint.

Ligaments

Lateral lumbosacral ligament: arises from the lower margin of the transverse process of L5 vertebra and passes obliquely inferiorly to attach on the ala of the sacrum.
The ligament is partially continuous with the iliolumbar ligament at its origin point and blends with the anterior sacroiliac ligament at its insertion on the sacrum.

Ligament Stability of the Lumbar Spine

The thoracolumbar fascia consists of three layers: the posterior, middle, and anterior.
The posterior layer is large, thick, and fibrous and arises from the spinous processes and supraspinous ligaments of the thoracic, lumbar, and sacral spines.

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Description

Learn about the curves of the spine, typical lumbar vertebrae, and their anatomic position. Understand the structure and function of the lumbar spine. Based on Neumann and Kapandji's works.